1. Field of the Invention
The present invention relates generally to an apparatus and a method for saving power of a mobile communication terminal in a mobile communication system, and more particularly to an apparatus and a method for saving power by quickly processing a message.
2. Description of the Related Art
Mobile communication terminals repeat a process of periodically awaking from an idle state according to a slot cycle index, checking their own slots, and then shifting to a sleep state again. For example, when a slot cycle index is 1, a period is 2.56 seconds.
More specifically, mobile communication terminals generally awake at their own slots, receive general page messages, and then sleep or sleep fast. However, sometimes mobile communication terminals receive overhead messages due to the change of base station (BS) information or a sequence. Further, sometimes mobile communication terminals receive Data Burst Messages (DBMs), order messages, Channel Assignment Messages (CAMs), Extended Channel Assignment Messages (ECAMs), etc.
Messages received from a base station (BS) are processed via an RX task, a layer 2 task, and a main control layer. In a mobile communication terminal, the RX task generates a 20 ms interrupt for the messages received from a base station (BS) and then transfers the interrupted message to an upper layer. When a paging channel data rate is 9600 bps, a 20 ms frame has a size of 192 bits and this frame is sent to an upper layer for processing.
Theoretically, the slot of a paging channel has a unit of 80 ms and a mobile communication terminal awakes for 80 ms slot. However, actually considering a period of time for which the mobile communication terminal awakes and prepares to sleep, the mobile communication terminal awakes for about 95 ms. Accordingly, when a slot cycle index is 1, the mobile communication terminal awakes for 95 ms every 2.56 seconds. This is associated with the battery consumption of the mobile communication terminal. That is, when the mobile communication terminal is awake for a long time, the battery consumption increases.
Typically, a mobile communication terminal receives many data burst messages, i.e., short message service (SMS) messages, through a traffic channel. The data burst message includes a data burst message (general data burst message) having a general address and a data burst message (broadcast data burst message) having a broadcast address. The former is received through a point-to-point scheme and the latter is received through a broadcast scheme. The general data burst message or the broadcast data burst message as described above is discarded or processed according to agreement or disagreement of an address. Herein, the agreement of an address means that an Electronic Serial Number (ESN)/phone number or a broadcast address of a mobile communication terminal included in a message transmitted from a base station (BS) is identical to those stored in a mobile communication terminal receiving the message. This enables the mobile communication terminal to recognize if the message transmitted from the base station is directed to the mobile communication terminal itself.
In the Republic of Korea, a typical SMS message capable of being transmitted by a general user once has a limited size of 80 bytes. Further, because a broadcast SMS message is also used when a base station (BS) provides a mobile communication terminal with information, the broadcast SMS message is generally transmitted after 80 bytes are completely filled with contents. Herein, when a mobile communication terminal receives a data burst message having such a size in an idle state, a layer 2 of the mobile communication terminal discards the data burst message by reason of the disagreement of an address. Because a message such as an ECAM/CAM and a command has a small size, the message may be processed in one frame. However, because the data burst message has a large size, unnecessary overhead occurs in an RX task and the layer 2 and a time point at which the mobile communication terminal enters a sleep state is also delayed. Therefore, the battery power is wasted.
More specifically, when a paging channel data rate is 9600 bps, a mobile communication terminal sends a message with 192 bits each time to the layer 2 task about six times. Then, all the sent bits are reassembled and whether their addresses agree with each other or not is examined. As a result of the examination, the mobile communication terminal discards the message when the message does not target the mobile communication terminal itself.
Accordingly, when an RX task generates many frames and sends the frames to a layer 2, a mobile communication terminal cannot process the frames while it awakes only for one slot. Further, under the environments of reception of many data burst messages, even though the mobile communication terminal is in an idle state, the power of the mobile communication terminal is greatly consumed.